Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753068Ab2EWFmq (ORCPT ); Wed, 23 May 2012 01:42:46 -0400 Received: from perches-mx.perches.com ([206.117.179.246]:50500 "EHLO labridge.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752082Ab2EWFmo (ORCPT ); Wed, 23 May 2012 01:42:44 -0400 Message-ID: <1337751760.13111.47.camel@joe2Laptop> Subject: Re: [PATCH] Add human-readable units modifier to vsnprintf() From: Joe Perches To: Kent Overstreet Cc: Tejun Heo , linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org, dm-devel@redhat.com, agk@redhat.com Date: Tue, 22 May 2012 22:42:40 -0700 In-Reply-To: <20120523052236.GA14312@dhcp-172-18-216-138.mtv.corp.google.com> References: <20120522211706.GH14339@google.com> <20120523031214.GA607@dhcp-172-18-216-138.mtv.corp.google.com> <1337744190.13111.33.camel@joe2Laptop> <20120523045023.GE607@dhcp-172-18-216-138.mtv.corp.google.com> <1337749848.13111.40.camel@joe2Laptop> <20120523052236.GA14312@dhcp-172-18-216-138.mtv.corp.google.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.2- Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1672 Lines: 50 On Wed, 2012-05-23 at 01:22 -0400, Kent Overstreet wrote: > On Tue, May 22, 2012 at 10:10:48PM -0700, Joe Perches wrote: > > On Wed, 2012-05-23 at 00:50 -0400, Kent Overstreet wrote: > > > diff --git a/lib/vsprintf.c b/lib/vsprintf.c > > [] > > > @@ -1002,6 +1023,7 @@ int format_decode(const char *fmt, struct printf_spec *spec) > > > case ' ': spec->flags |= SPACE; break; > > > case '#': spec->flags |= SPECIAL; break; > > > case '0': spec->flags |= ZEROPAD; break; > > > + case 'h': spec->flags |= HUNITS; break; > > > default: found = false; > > > } > > > > > > > I think that doesn't work well because > > gcc __attribute__((format(printf, x, y))) > > verification fails. > > Yeah, I already ran into that. I was looking through the gcc docs to see > if there was a way to add modifiers (how is it done for the other kernel > specific format strings?) but I haven't found anything yet It's done via %p extensions. gcc doesn't care as long as the %p argument is a pointer. > > It's also possible > > to confuse it with printf's own 'h' / > > integer precision use. > > Well, that's annoying. Any suggestions? I gave you one already. Use a new lib/vsprintf.c %p pointer extension like "%pD" or "%pH" and use a pointer to the type as the argument. It's how it's done for an ipv4 address. For instance: be32 address = cpu_to_be32(0xc0a80101); printk("%pI4" &address); emits "192.168.1.1" -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/